Friday, August 7, 2009

PM Update: U.S. Has 27th Coolest July

For Washington, DC July temperature analysis, see:
Washington Has 44th Coolest July
For previous record temperature posts, see:
Record Heat
Record Cold

The National Climatic Data Center's (NCDC) preliminary analysis for July, posted this afternoon, indicates that the past month was the 27th coolest out of 115 years of record in the U.S. The national average temperature of 73.5°F was 0.8°F below the 20th century average. For the year to date (January through July), on the other hand, the average was the 28th warmest.

The cool temperatures were particularly acute in the Midwest and Ohio Valley, where 6 states had their coolest July on record: Iowa, Illinois, Indiana, Ohio, Pennsylvania, and West Virginia. In addition, several adjoining states had their second coolest July: Wisconsin, Michigan, Missouri, and Kentucky.

Temperatures were above normal from Florida westward across the Southwest, California, and the Pacific Northwest. Arizona had its third warmest July, and temperatures were also much above normal in New Mexico and Washington. NCDC reports that "Death Valley, California set its all-time monthly average maximum temperature of 121.3°F. Twenty-two days in Death Valley reached 120°F or higher which beat the old record of 19 days."

The temperature pattern of cold in the Midwest and Northeast and warm in the West was the result of a persistent, abnormally strong, circulation pattern in the middle levels of the atmosphere which had a low pressure trough centered near the Great Lakes and a high pressure ridge along the Pacific Coast.

Other temperature highlights from NCDC:
  • "The U.S. had not seen a single record cold state, in any month, since August 2004 and there had not been six or more record cold states in a month since July 1992, when there were nine."
  • "More than 400 record low minimum temperatures and 1,300 record low maximum temperatures (lowest high temperature) were set during July across the nine-state area that makes up the Central region."

Images (click to enlarge): July 2009 temperature departure from average, statewide temperature rank, 500 mb heights and departures from average, from NOAA/NCDC

No comments:

Seasonal Outlook

Latest seasonal forecast: Click here.

Latest 3-month temperature outlook from Climate Prediction Center/NWS/NOAA.